Lack of correlation between BCG-induced tuberculin skin test sensitisation and protective immunity in cattle

► The duration of BCG-induced tuberculin skin-test sensitisation was determined in neonatally vaccinated calves. ► BCG induced strong skin-test sensitisation in calves but this sensitisation waned rapidly after 6 months. ► Groups of BCG vaccinated calves that had lost or retained their skin-test response after 6-months were challenged with M. bovis to investigate the relationship between skin-test sensitisation and vaccine induced protective immunity. ► Loss of BCG induced skin-test responsiveness did not result in loss of protective immunity against M. bovis infection.